Can someone
a flight of stairs is supported by two columns, as shown in the diagram.
the distance from the base of the stairs to the taller column feet.

The two triangles are similar triangles. 
The smaller triangle has hypotenuse 6 and a horizontal leg of 4
The large triangle has hypotenuse 6+12=18 and a horizontal leg of x, where x is some number larger than 4

Because the triangles are similar, we can form the proportion below and solve for x
x/4 = 18/6
6*x = 4*18
6*x = 72
6*x/6 = 72/6
x = 12

Final 12